Kobo director of merchandising Nathan Maharaj pointed out that DRM that restricts books to one particular class of device runs up against the mom problem: non-tech-savvy moms are an important e-book market, and making it possible for them to read e-books easily on any device they have will help to capture that market.

But at the moment, Maharaj noted, evidence is thin on the ground as to whether DRM-free e-books really do sell better. More data may be needed, and it may have to wait for the launch of the extremely popular DRM-free Harry Potter series to provide that evidence.